Re: [Xen-devel] [PATCH 2/2] x86/VMX: don't needlessly install VMFUNC emulation hook

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 22/12/16 08:37, Jan Beulich wrote:
> Instead of checking cpu_has_vmx_vmfunc inside the hook, use it to
> determine whether to install the hook in the first place.
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
I am not so sure about this.

vmfunc is reachable in the instruction emulator on hardware which 
doesn't support vmfunc, and there is explicit provision for using vmfunc 
0 via hypercall on hardware lacking vmfunc support.
Given that the #VE part of altp2m is always emulated architecturally, I 
think there is an argument to be made for also emulating EPTP switching 
architecturally as well.
~Andrew

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